The present invention relates to an image recording apparatus such as a copying machine or a printer. Further, relating U.S. Patent applications have been filed bearing Ser. Nos. 281,336 (corresponding to Japanese Utility Model Application No. 62-189349) filed on Dec. 8, 1988, and Ser. No. 281,215 (corresponding to Japanese Utility Model Application Nos. 62-191014 and 63-17646) filed on Dec. 8, 1988.
A commonly assigned copending U.S. Patent application Ser. No. 244,681 has been filed on Sept. 14, 1988 which discloses an image recording apparatus having an exposure unit, an optical system, and a developing unit. This copying machine employs a transfer type image recording mediums such as a photosensitive sheet which comprises a microcapsule sheet (first image recording medium) and a developer sheet (second image recording medium). More specifically, in the transfer type recording mediums, the developer material is coated on a separate substrate as a separate developer or copy sheet. The first image recording medium comprises a photosensitive pressure sensitive recording medium provided with microcapsules which encapsulate therein a first material (chromogenic material or dye precursor) having first and second phases dependent on light exposure. The second image recording medium comprises the developer medium provided with second material (developer material) which provides an output image upon reaction with the first material. Such image recording medium is disclosed in, for example, U.S. Pat. No. 4,399,209 and Japanese Patent Application Kokai No. 58-88739.
The image recording apparatus disclosed in the copending U.S. Patent Application is shown in FIG. 1 which generally includes a main frame 140, an exposure unit E for exposing photosensitive pressure sensitive image recording medium 137 to light by means of an optical system L at an exposure zone 119 so as to form a latent image corresponding to an original (not shown) on the recording medium 137, a pressure developing unit 120 for pressure developing the recording medium 137 which carries the latent image, and sheet feeding means F including feed rollers 150 for feeding the recording medium 137 from the exposure unit to the pressure developing unit 120.
At an upper portion of the apparatus, an original cover member 101 and an original support glass 102 for mounting thereon an original (not shown) are disposed which are movable in horizontal direction indicated by arrows A and B. The optical system L is positioned below the original support glass 102. The optical system L includes a light source 103, a semi-cylindrical reflector 104, a plane reflector 105, a first reflection mirror 111a, a shutter 116, a lens unit 109, a filter 108, and a second reflection mirror 111b. The semi-cylindrical reflector 104 is positioned behind the light source 103 so as to direct light toward the original, and the plane reflector 105 is adapted to reflectingly direct the light toward the original from the light source which light originally has not been directly directed toward the original. The first reflection mirror 111a is adapted to direct light reflected from the original toward the shutter 116, the lens 109 and the filter 108, with providing a first optical axis having a light path length L1 between the first reflection mirror 111a and the shutter 116. The second reflection mirror 111b is adapted to direct light passing through the filter 108 toward the exposure zone 119. A second optical axis having a light path length L2 is defined between the filter 108 and the second reflection mirror 111b.
At a lower portion of the apparatus, a phOtosensitive sheet roll cartridge 113 is disposed whose upper surface serves as the exposure zone 119. The photosensitive pressure sensitive recording medium 137 accommodated within the cartridge 113 is pulled out of the cartridge 113, and is promptly subjected to light exposure at the upper surface of the cartridge 113. In this case, the photosensitive sheet 113 is continuously moved in synchronism with the horizontal movement of the original support glass 102 in the direction indicated by the arrow B, and therefore, a latent image corresponding to the original is successively formed on the photosensitive sheet 137.
The pressure developing unit 120 is disposed below the optical system L and beside the sheet roll cartridge 113 at downstream side thereof with respect to a sheet path. Further, a developer sheet cassette 132 is disposed below the developing unit 120 so as to supply each one of a developer sheet 138 at an inlet portion of the developing unit 120. At the inlet portion, the developer sheet 138 is superposed with the photosensitive sheet 137 which carries the latent image, and the thus superposed sheets 138 and 137 are subjected to pressure at the developing unit 120, so that developed image is provided on the developer sheet 138.
A take-up means 125 is disposed beside the optical system L so as to wind the light-exposed photosensitive sheet 137 thereover. Further, separation unit 123 is disposed at downstream of the developing unit 120 so as to separate the developer sheet -38 from the photosensitive sheet 137. Furthermore, a thermal fixing unit 142 is disposed at downstream side of the separation unit 142. The thus separated developer sheet carrying the developed image thereon is subjected to thermal fixing operation, so that a final visible image is provided on the developer sheet 138.
According to the image recording apparatus disclosed in the copending U.S. Patent Application, the following disadvantages may be conceivable:
When assembling the optical system L into the apparatus, securing positions of the first and second reflection mirrors 111a and 111b must be finely adjusted independent of each other so as to finally provide an optimum optical axes L1 and L2. Further, in order to adjust focussing length of the lens unit 109, relative positional relationship between the dense unit 109 and the reflection mirrors must be further adjusted. However, since the adjustment requires positional or angular orientational changes of the reflection mirrors 111a and/or 111b, exposure position at the exposure zone 119 may be deviated, and therefore, latent image may not be formed at a proper position on the photosensitive pressure sensitive sheet 137.
The optical axes L1 and L2 defined by the above described optical system L must be oriented in given directions with respect to the moving directions A and B of the original support units 101 and 102 so as to avoid degradation of image-resolution power. With the structure, the main frame 140 may be distorted, if a heavy original such as an encyclopedia is mounted on the original support glass 102 for a page copying, or if such heavy member is mounted on the upper portion of the main frame 140, or if inadvertent load or impacting force is applied externally to the main frame 140. However, as described above, since the optical system is disposed along the directions A and B at the upper portion of the apparatus, the optical system per se is also subjected to distortion due to the mechanical deformation of the main frame 140. As a result, the optical axes L1 and L2 may be deviated from their correct positions, to thereby disadvantageously provide defocussing, to thus cause degradation of the resolution power.
Further, as described the above, the developer sheet 138 carries the developer medium reactable with the chromogenic material of the microcapsule sheet 137. When the developer sheet 138 passes through the pressure developing unit 120 and the thermal fixing unit 142, part of the developer material may be released from the developer sheet due to frictional contact with these units, and the thus released developer material may be in the particulate forms. As is well known, the pressure developing unit 120, the thermal fixing unit 142 and other unit such as a driving unit (not shown) may release heat, and the light source 103 generates a radiant heat. Therefore, such heat may generate air convection, so that the particles of the developer materials may fly upwardly, and the particles may be accumulated on the components of the optical system L. As a result, resolution power may be degraded or lowered.
Furthermore, with the structure disclosed in the copending application, the photosensitive pressure sensitive sheet 137 is initially pulled over the upper surface of the sheet roll cartridge 113 for light exposure, and the thus exposed sheet 137 is then delivered to the pressure developing unit 120 through a sheet path provided by the feed rollers 150. Since the feed rollers 150 are each disposed alongside the sheet roll cartridge 113, excessive length of the photosensitive pressure sensitive sheet 137 is required so as to provide a single image thereon, which length greatly exceeds a length of a final output image. More specifically, in order to obtain an image, bridging over the exposure zone 119, other sheet lengths are required which extend along the side surfaces of the sheet cartridge 113 so as to allow the sheet 137 to reach the pressure developing unit 120. Accordingly, the sheet 137 is disadvantageously wasted.